Biodegradation of Polystyrene by Dark (Tenebrio obscurus) and Yellow (Tenebrio molitor) Mealworms (Coleoptera: Tenebrionidae)

Yellow mealworms (larvae of Tenebrio molitor, Coleoptera: Tenebrionidae) have been proven to be capable of biodegrading polystyrene (PS) products. Using four geographic sources, we found that dark mealworms (larvae of Tenebrio obscurus) ate PS as well. We subsequently tested T. obscurusfrom Shandong, China for PS degradation capability. Our results demonstrated the ability for PS degradation within the gut of T. obscurusat greater rates than T. molitor. With expanded PS foam as the sole diet, the specific PS consumption rates for T. obscurusand T. molitorat similar sizes (2.0 cm, 62–64 mg per larva) were 32.44 ± 0.51 and 24.30 ± 1.34 mg 100 larvae–1d–1, respectively. After 31 days, the molecular weight (Mn) of residual PS in frass (excrement) of T. obscurusdecreased by 26.03%, remarkably higher than that of T. molitor(11.67%). Fourier transform infrared spectroscopy (FTIR) indicated formation of functional groups of intermediates and chemical modification. Thermo gravimetric analysis (TGA) suggested that T. obscuruslarvae degraded PS effectively based on the proportion of PS residue. Co-fed corn flour to T. obscurusand wheat bran to T. molitorincreased total PS consumption by 11.6% and 15.2%, respectively. Antibiotic gentamicin almost completely inhibited PS depolymerization. High-throughput sequencing revealed significant shifts in the gut microbial community in both Tenebriospecies that were associated with the PS diet and PS biodegradation, with changes in three predominant families (Enterobacteriaceae, Spiroplasmataceae, and Enterococcaceae). The results indicate that PS biodegradability may be ubiquitous within the Tenebriogenus which could provide a bioresource for plastic waste biodegradation.